IJIREEICE
ISSN (Online) 2321 – 2004
ISSN (Print) 2321 – 5526
INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN ELECTRICAL, ELECTRONICS, INSTRUMENTATION AND CONTROL ENGINEERING
Vol. 4, Issue 5, May 2016
Simulation and Controlling the Speed of
Electric Locomotive through PWM Technique
Arvind Kumar Verma1, V.K Tripathi2
PG Student, Department of Electrical Engineering, SHIATS, Allahabad (U.P.), India1
Asst. Professor, Department of Electrical Engineering, SHIATS, Allahabad (U.P.), India2
Abstract: Motion control plays a very important role in traction purposes. Different type of motors AC & DC are used
depending upon the type of traction. DC motors are used in many industrial and commercial applications require higher
performance, reliability, variable speed and so on due to ease of controllability. DC motor are widely used because of
easier controlling, whose speed is directly proportional to the supply voltage. Using this relationship between the speed
and the supply voltage, in this paper mainly focused on the simulation of a pulse width controlled direct current motor
using Simulink environment in MATLAB for Electric Locomotive Control.
Keywords: Traction, DC motor, PWM, Matlab, Simulink, Locomotive.
1. INTRODUCTION
Traction motor refers to an electric motor providing the
primary rotational torque of a machine, usually for
conversion into linear motion (traction).Electric
locomotives generally have two or more AC or DC
motors. In these locomotives, power is collected from an
Electric trolley which is running on an overhead wire. The
overhead wire can carry both types of supply AC as well
as DC. Indian railway also used both types of supply
systems:
a) AC System- 25 KV single phase and three phase 50 Hz
AC supply.
b) DC System- 1500V DC supply (only western zone &
central zone of railway).
c) Mixed type Locomotives(AC traction with DC drives).
In this paper there is mainly focus on the mixed type
locomotives. Where the 25 KV AC supply is used to drive
the DC series motors through a converting applications.
The first AC traction is introduced in 1959, namely
(WAM series) uses DC locomotives of 2800 HP with a
four water colled ignitrons rectifiers, they were mostly
developed by ER (Eastern Railway) in the HowrahAsansol-Dhanbad-mughalsarai section of the Central
Railway, but the ever best WAM series
manufactured by Alstom/CLW (575 KW/770 HP, 750V,
1095 rpm each) Axle-hung, nose suspended, force
ventilated motors. They were two silicon rectifiers are
used. They have many more WAP-series traction motors
namely WAP-2, WAP-3, WAP-4, WAP-5, WAP-6 and
WAP-7. Now the days WAG and WAP series locomotives
are much more efficient for the fright and passenger trains
WAP-4 and WAP-6 D.C locos were much more used in
Indian traction purposes with the use of Thyristor control
techniques. The WAP-5 and WAP-7 is now converted
from DC traction to AC traction because of the new
control strategies were used to control the AC power. In
this paper the main purpose of introduce about the DC
traction series because the control methods of DC is made
much more efficient and reliable at place of AC
locomotives because the uses of GTO’s and other
electronic controllers are made the system more
expensive.
2. D.C MOTOR
Locomotive is WAM-4 introduced in 1970-72 the WAM-4
model was produced; the first indigenously designed and
built electric loco (the first delivered by CLW). They were
produced until about 1997.Thelocomotive is named as
WCM 5(built in 1962, by Chittaranjan locomotive works
to RDSO’s design specification) 3700 HP co-co. And
WCM 6 (5000 HP were built in 1995 by CLW).
Then in the 80’s the new era of electric locos were
introduced with WAP-series locomotives by RDSO design
specifications, the locos were at first used solely for the
Howrah-Delhi Rajdhani, It was haul the 18-coach at a
max. Speed of 120 km/h and an average speed of around
82km/h. Continuous power 3760 HP, the motor were
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Fig 2 (a) Sketch review of dc series motor
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239
IJIREEICE
ISSN (Online) 2321 – 2004
ISSN (Print) 2321 – 5526
INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN ELECTRICAL, ELECTRONICS, INSTRUMENTATION AND CONTROL ENGINEERING
Vol. 4, Issue 5, May 2016
The DC traction motors is a four pole DC series motor in
which field winding is connected in series with the
armature. It is a forced ventilated machine arranged for
axle mounting on sleeve bearing. Transverse movement is
limited by flanges of axle suspension bearings. The D.C
series motor is high starting torque, vibration free
machine.
wave can be changed. Variable voltages can also be
generated by using fixed pulse width but varying instead
the pulse Amplitude (Pulse Amplitude Modulation-PAM)
or the pulse repetition frequency (pulse frequency
modulation-PFM).
3. THE DC TRACTION MOTOR: HOW IT DRIVES
THE AXLE
Basically the shaft of locomotive of electric traction is
fitted with the motor pinion (armature drive shaft) which is
directly drive the gear of Axle. The hole arrangement of
armature drive shaft is interlocked with traction motor
case as shown in the fig 3 (a).
5.1 Principle
The main principle is control of power by varying the duty
cycle. Here the conduction time to the load is controlled
by,
Let
For a time t1, the input voltage appears across the load i.e.
ON state.
For t2time the voltage across the load is zero.
The average voltage at output is given by
Va= 1/T ʃ Vo dt = t1/T
Vs = ft1Vs = kVs
The average load current
Ia = Va/R = KVs/R
Where T is the total time period = t1+t2
k = t1/T is the duty cycle
Fig 3 (a) DC Motor drive the axle through a
The RMS value of output voltage is
Pinion and gearwheel
Vo = ( i/T ʃ Vo2 dt )1/2 = K Vs
The output power is given by
4. SPEED CONTROL OF DC MOTOR
Pi = 1/T ʃVoidt = 1/T ʃ Vo2/R dt = kVs2/R
The purpose of the motor speed controller is to take a The duty cycle can be varied from 0 to 1 by varying t 1, T
single representing the required speed, and to drive a or f. Therefore, the output
motor at that speed. Motor speed can be controlled by
controlling Armature voltage(Va)
 Armature current(Ia)
It is obvious that the speed can be controlled by varying
 Flux/pole, Φ (flux control)
 Resistance of armature (Ra) circuit (Rheostatic control)
 Applied voltage V (voltage control)
5. PWM TECHNIQUE
Fig 5.1 (a) Duty cycle Ratio
PWM (pulse width modulation) is a method for binary
signals generation, which has two signal periods (high and Voltage Vo can be varied from 0 to Vs by
low). The width (W) of each pulse varies between 0 and Controlling k, and the power flow can be
the period (T). The duty cycle (D) of a signal is the ratio of Controlled.
pulse width to period.
6. BASIC CIRCUIT
D=(t +t )/T
1
2
AC voltages can be similarly controlled using bidirectional pulses to represent the sinusoidal. Wave
Various PWM schemes are possible. Only one is shown
here. By varying the pulse width, the amplitude of the sine
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The basic circuit consists of a 25 KV AC. Pantograph with
a tap changer step down transformer, a set of rectifiers is
used to convert the single phase AC supply to a ripple less
DC to drive the DC locos.
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IJIREEICE
ISSN (Online) 2321 – 2004
ISSN (Print) 2321 – 5526
INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN ELECTRICAL, ELECTRONICS, INSTRUMENTATION AND CONTROL ENGINEERING
Vol. 4, Issue 5, May 2016
7.2 The Buck Converter
The Buck Converter is a form of DC to DC converter that
can take an input directly from a DC source, such as
battery. The input could also be DC derived from the AC
mains (line) via a rectifier/reservoir capacitor circuit.
Fig 6 (a) Basic Electric traction outline diagram
7. MATLAB SIMULATION
Computer modeling and simulation tools have been
extensively used to support and enhance electric
machinery courses. MATLAB with its toolboxes such as
Simulink and sim power system is one of the most popular
software packages used by educators to enhance teaching
the transient and steady-state characteristics of electric
machines.
The simulation is done on the basis of the pulse width
modulation technique in the drive circuit. The basic circuit
of this simulation consist block of a subsystem, a buck
converter, a DC motor block, a disturbance block &a
scope (to see the simulation results).
Fig 7 (a) Model created in SIMULINK Toolbox of
MATLAB
7.1 The Sub System
The Sub System consists of a pulse generator input of the
percentage duty cycle to be feed for buck converter.
Fig 7(b) pulse generator of sub system
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Fig 7 (c) DC to DC Buck Converter
As shown in the fig the buck converter consists of a the
switching transistor, together with the flywheel circuit
(D1, L1 and C1). While the transistor is on, current is
flowing through the load via the inductor L1. The action of
any inductor opposes changes in current flow and also acts
as a store of energy. In this case the switching transistor
output is prevented from increasing immediately to its
peak value as the inductor stores energy taken from the
increasing output; this stores energy is later released back
into the circuit as a back e.m. fas current from the
switching transistor is rapidly switched off. Here the use
of continuous mode of operation to drive the locomotive
continuously. It is made by if the current through the
inductor (L) never falls to zero during the commutation
cycle.
7.3 Disturbance at Plant Input
Step time, initial values, final values, sample time etc
which are very useful and the system make reliable to
operate but it generates some noise in the system, which
are conclude as a disturbance but there are very small
disturbances occurs by this parameters, So here we keep
these parameters, constant or zero.
7. 4 DC Motor
This block is mainly consisting of the motors parameter
like damping, inertia, back e.m.f, resistance and
inductance of the motor. The output voltage of the buck
converter is fed in this block to draw the graph of speed
and input voltage waveform of the motor.
Fig 7 (d) State Space block of the DC Motor
DOI 10.17148/IJIREEICE.2016.4560
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IJIREEICE
ISSN (Online) 2321 – 2004
ISSN (Print) 2321 – 5526
INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN ELECTRICAL, ELECTRONICS, INSTRUMENTATION AND CONTROL ENGINEERING
Vol. 4, Issue 5, May 2016
This above (A,B,C,D) parameters is set by using double Now again the simulation is done at the 40% duty cycle,
clicking on the D.C motor block to appear the dialog box and the damping ratio upto 0.272.
of the system.
7.5 Scope
This is the display unit of the hole simulation and shows
the graph of speed-torque and the output voltage of the
buck converter circuit as later discussed, it has consist of
two axis (x & y) for each measuring parameter the number
of display units are extend by simply change in settings of
scope.
8. SIMULATION RESULT& DISCUSSION
The basic simulation of DC locomotive is carried by
updating the value of PWM duty cycle at proper extent,
because the applied voltage can be varied by changing the
duty cycle of PWM generator. The ratio of T on to Toffis
must to change with respect to time. Now first we observe
the simulation result without setting the A, B, C, D
parameters of DC Motor. This simulation is mainly shows
the basic speed characteristic of WAP 6 (DC) locomotive.
Fig 8 (c) 40% Duty cycle applied to drive
The above block shows the PWM duty cycle in
percentage. This means the applied voltage is ON for 40%,
and OFF for 60% out of 100% supply voltage, Means we
can also say that the speed of DC motor behind the PWM
control technique is below the maximum speed of the
motor. At 40% the voltage is around 93.61 to 93.615V.
Fig 8 (a) Basic voltage and speed characteristics
Now again we conclude the parameters of drive to get
some desirable values of speed, and applied voltage.The
upper half of the graph shows the applied voltage
waveform and lower is speed characteristics of the DC
loco. The following graph is of the 20% duty cycle ratio,
and mutual inductance (L) is set to 2.621. Where the
Fig 8 (d) Parameters block of D.C drive
resistance of the field and armature winding of the motor
is set to150 ohm, whereas the inertia of the drive is 15 The above block shows the parameter of the DC motor
kg*m2.
which is set to simulation at 90% PWM duty cycle, the
90% duty cycle take the voltage at 412.64V
Fig 8 (e) 90% Duty cycle applied to system
Fig 8 (b) voltage and speed characteristics after 20%
PWM applied
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The 90% duty cycle ratio gives the voltage around the
maximum speed of the drive
DOI 10.17148/IJIREEICE.2016.4560
242
IJIREEICE
ISSN (Online) 2321 – 2004
ISSN (Print) 2321 – 5526
INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN ELECTRICAL, ELECTRONICS, INSTRUMENTATION AND CONTROL ENGINEERING
Vol. 4, Issue 5, May 2016
Fig 8 (f) Voltage at 90% Duty cycle
9. CONCLUSION
In this paper, the simulation of a PWM control techniques
of a D.C Motor is developed using MATLAB/Simulink.
The Simulation result shows that the applied voltage on
the Motor is directly proportional to the speed of the
motor. So the PWM technique is so reliable to control the
D.C locomotives and gives variable speed as operator
premises. It’s have better future scope in upcoming high
speed trains and also the operational cost is so much
reduceable.
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BIOGRAPHY
Arvind Kumar Verma received the
B.Tech
Degree
in
Electrical
Engineering from UPTU, Lucknow in
2014. Now he is pursuing his M.Tech in
Electrical Engineering (Control &
Instrumentation) from Department of
Electrical
Engineering,
SHIATS,
Allahabad (UP), India.
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